A number of congenital defects are encountered in pediatric cardiac surgery wherein it is desirable to create a passageway between adjacent vessels or adjacent regions of an organ. For example, congenital lesions frequently involve an obstruction of blood flow to the lungs, such as pulmonary atresia with, or without intact ventricular septum, Tetralogy of Fallot, complex single ventricle anatomy, and pulmonary valve stenosis.
A first step in treating such defects typically involves placing a graft between the systemic arterial system and the pulmonary arteries to supply blood to the lungs. Such a graft is often referred to as "Blalock-Taussig shunt" or "B-T" shunt, and is placed between the native subclavian artery and the pulmonary artery. To install a typical Blalock-Taussig shunt, the surgeon exposes the mediastinum (the contents of the middle of the chest between the two lungs), the pulmonary artery and the subclavian artery. A graft of suitable synthetic material (e.g., PTFE) is then anastomosed between the arteries, so that flow passes from the subclavian artery to the lungs via the pulmonary artery.
In the Glenn procedure, often performed as the second stage of treating pulmonary atresia and single ventricle anatomy, the distal end of the superior vena cava is anastomosed to the superior wall of the right pulmonary artery, while the proximal end of the superior vena cava is either occluded or anastomosed to the inferior wall of the right pulmonary artery. It would therefore be desirable to provide apparatus to percutaneously anastomose the pulmonary artery to the superior vena cava.
In the Fontan procedure, which is often used to treat complex single ventricle anatomy, the proximal end of the superior vena cava is anastomosed to the inferior wall of the right pulmonary artery, and the right atrium closed off, so that there is little or no communication between either the inferior vena cava or the superior vena cava and the right atrium. Isolation of the vena cava from the right atrium also minimizes the impact of an atrial septal defect. Conventional treatment of single ventricle anatomy is generally performed in two surgical stages, to enable the heart to gradually accommodate the hemodynamic impact of the procedure. However, repeated surgeries cause significant trauma to the patient, require long recuperation times, and pose serious risks of mortality. It therefore would be desirable to enable at least one stage of a complicated procedure, such as the Glenn or Fontan procedure, to be accomplished using an interventional (i.e., percutaneous), rather than surgical, approach.
In other medical applications, such as treatment of coronary artery disease and in some cases of pulmonary vascular atresia, it is often desirable to form a passageway through an occlusion. Unfortunately, balloon dilatation catheters generally can only be used where there is not total occlusion, while cutting catheters, such as atherectomy catheters, pose a risk of dissecting the vessel. It would therefore be desirable to provide apparatus and methods that would enable an opening to be formed through an occluded pulmonary valve or occluded vessel with a high degree of certainty of the trajectory of the puncture.
In view of the foregoing, it would therefore be desirable to provide apparatus that enables the formation of a passageway between adjacent vessels, adjacent regions of an organ, or between an organ and an adjacent vessel, to establish a flow path therebetween.